Filters
Filters add effects to a layer: blurs, shadows and glows, colour changes and outlines. They stack in a list, and every setting of every filter can be animated.
Step by step
Select the moon
Click the moon on the canvas, or its row in the Layers panel.
Open the filter menu
In the inspector's Filters section, click + Add filter…. The menu has three groups: Blur & shadow, Color and Edges.
Pick Glow
Click Glow. It appears as a card with its settings (X, Y, Blur, Spread, Color and Opacity), and the moon glows.
Start a Spread track
Click beside the glow's Spread. It gets its own row on the timeline, with a keyframe at the playhead.
Move the playhead to 2s
Drag the red playhead along the time ruler to 2s.
Widen the glow
Type 12 in Spread and press Enter. A second keyframe lands at 2s, and the glow grows into a wide halo.
Play it
Press Space. The glow swells for two seconds, rests, and starts over. Filters animate in the JavaScript export; a CSS export keeps them still, as the note in Filters says.
Keys
| Space | Play and pause |